This invention relates to a push button electrical switch and in particular, to a low cost push button switch which has a long life and which is reliable in operation.
Push button electrical switches are well known in the prior art and are used in a variety of applications, such as, for instance, in automotive applications for controlling one or more low voltage circuits.
U.S. Pat. No. 3,694,603 discloses a push button switch including an indexing movement wherein operation of the push button causes a conductive contactor to move axially and, at a particular axial position, to bridge two terminals for completing the circuit.
One problem with this prior art push button switch is the fact that, if the switch is in its closed state, only a small amount of movement of the push button will cause the contactor to move axially out of contact with the terminals, thereby immediately breaking the electrical circuit. Thus the push button may be manipulated by the operator, or in certain situations, may be operated by vibrations of the equipment in which the switch is mounted, to cause the switch to open without positive and complete actuation of the switch. It is therefore desired to provide a push button electrical switch wherein the closing and opening of the switch is positively controlled, thereby preventing accidental or intermittent opening of the switch.
A further problem with the aforementioned prior art push button switch is the fact that the push button has two rest positions. In a first position, when the switch is closed and the contactor bridges the terminals, the push button is in its uppermost rest position. When the push button is actuated in order to open the switch, the contactor is axially positioned to remain out of contact with the terminals whereby the push button itself occupies an axially different rest position than in the closed position of the switch. This is undesirable in certain applications when it is desired that the push button occupies the same rest position regardless of whether the switch is in its closed or open state.
A still further problem with the aforementioned prior art push button switch is that it is subject to excessive wear and therefore has a limited life. This wear is due to the fact that the contactor operates linearly axially and always contacts the same contact points on the terminals. This causes arcing of the contacts, thereby removing metal from the contact points and also causing deposits to be formed on the contact points. Eventually, the contact points will be worn or deposits will accumulate to such an extent that high electrical resistance is built up at the contact points of the contactor and terminals. Alternatively, contact may even be entirely prevented thus causing complete failure of the switch.
It is therefore desired to provide a compact electrical push button switch which is not subject to wear because of arcing and therefore has a long life as compared to the above mentioned prior art switch and requires positive push button operation for the switch to change states. Furthermore, it is desired to provide a push button switch wherein the push button always returns to the same position.